Asymmetric electrode system



Sept. 27, 1938. J, H, DE 505g 2,131,1671

ASYMMETRI C ELECTRODE SYSTEM Filed Nov. 20, 1956 INVENTOR JAN HENDRIK DE sol 2R Patented Sept. 27, 1938 UNITED STATES ASYMM'ETRIC ELECTRODE SYSTEM Jan Hendrik de Boer, Eindhoven, Netherlands, assignor to N. V. Philips Gloeilampenfabrie ken, Eindhoven, Netherlands Application November 20, 1936, Serial No. 1 11,866 In Germany November 22, 1935 6 Claims.

This invention relates to electrode systems with unsymmetrical conductivity such as are used, for instance, in rectlfiers and photoelectric cells, wherein one of the electrodes consists for the greater part of selenium which is bounded by an insulating coating on one side.

In such electrode systems, wherein the semiconductor selenium constitutes one of the electrodes, it is very dimcult to provide the selenium on a support in such a manner that-it firmly adheres to the material of the support. Difllculties'are involved, among other things, in ensuring an intimate contact, since the selenium, which is usually applied in the liquid state, has the property of contracting to a drop.

For this reason it has already been proposed to provide selenium in selenium rectifiers on one of the metals of the iron class so as to ensure firm adherence of the selenium to the support.

However, this has the drawback that due to the high temperature at the limiting surface between the selenium and the support a compound of these two materials may ensue which may have insulating properties and form an insulating coating between the selenium and its support. However, the insulating coating proper, which may be formed genetically, is to be establishedon the other side of the selenium layer. Due to this the rectifying effect is almost completely neutralized or at any rate greatly reduced, since in this case there are two cells connected in opposition to each other. a

It is the principal object of my invention to provide an improved form of an electrode system having unsymmetrical, conductivity and using selenium as one of its constituents.

According to the invention these difliculties above are avoided by applying the selenium n a layer of amalgam preferably obtained by making the support from'any metal that can be amalgamated and amalgamatingit at least on' the side where this metal contacts with the selenium.

- In this'manner the information of an insulating is avoided at the contact In one particular embodiment ofthe inven-.

tion the support is made from amalgamated brass.

Again the support may advantageously consist of copper and also of aluminum. Since copper is an excellent thermal conductor a rectifier can be built in this case without separate plates for thermal radiation being necessary which are very cumbersome and by which the weight would be greatly increased. This is more particularly of. importance in rectifiers for high powers.

Aluminum has the advantage that when the support is made therefrom the aggregate is very light and in addition it allows of easily carrying off heat, so that in a high tension rectifier, for instance, which must consequently consist of a large number of series-connected units, a considerable saving in weight is ensured.

Hereinafter the manufacture and construction of an electrode system according to the invention will be more clearly explained by reference to the accompanying drawing representing one example thereof.-

By the action of a quantity of mercury spread on the surface of a brass support I an amalgam layer 2 is formed on to which molten selenium is applied which is painted out and smoothly rolled down to a thickness of 0.1 mm. For increasing the conductivity, this selenium may be mixed with other substances, for instance 2% of mercuric chloride (HgCl-z) or about 2% of calcium tungstate (CaWo4) The selenium layer 3 is converted into'the conductive crystalline modification by heating to about 200 C. for about 24 hours. On to this selenium layer 3 is applied the insulating coating 4 of polystyrene, which may be efiected with the aid of a solution of polystyrene in benzene. After that the assembly is heated again to about 200 C. for some hours, in order that the benzene shall be completely vaporized and the polystyrene thoroughly polymerized, thus increasing the density of this-,material and improving its favorable dielectric properties.

After that an electro-positive electrode 5 constituted by a layer of Woods metal is provided in the liquid state. In the present case the polystyrene serves at the same time as an adhesive for Woods metal. Tothis electrode is secured a connecting wire 6 which may be effected by soldering. l

The heating times referred .to in this example may be very difierent, for instance, in accordance with the substances -added to the selenium.

While I have indicated the preferred embodiments of my invention of which I am now aware and-have also indicated only one specific application for which my invention may be-employed,

' it will be apparent that my invention is by no means limited to the exact iorms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims. v

what I claim as new is:

1. An electrode system of unsymmetrical conductivity including any metal base which can be amalgamated and a layer of selenium on said base and an amalgam layer of said metal base between said base and said layer of selenium.

- 2. An electrode system of unsymmetrical conductivity including any metal base which can be amalgamated, a layer of amalgam of said metal base on said metal base, a layer of selenium on said amalgam, and an insulating coating on said selenium.

3. An electrode system 01. unsymmetrical conductivity including a brass base, an amalgam layer of brass on said base, a selenium layer on said amalgam layer, and an insulating coating on said selenium.

4. An electrode system of unsymmetrical conductivity including a copper base,,an amalgam layer of copper on-said base, a selenium layer on said amalgam layer, and an insulating coating on said selenium.

5. An electrode system of unsymmetrical conductivity including an aluminum base, an amalgam layer of aluminum on said base, a selenium layer on said amalgam layer, and an insulating coating on said selenium.

6. An electrode system of unsymmetrical conductivity including any metal base which can be amalgamated, an amalgam layer of said metal base on said base. a layer of selenium on said.

amalgam, and an insulating coating on said selenium, and an electrode on said insulating coating.

JAN 'HENDRIK a: BOER. 

